department of veterinary gynaecology...

M.J.F COLLEGE OF VETERINARY & ANIMAL SCIENCE,CHOMU, JAIPUR (RAJ.)

DEPARTMENT OF VETERINARY GYNAECOLOGY & OBSTETRICS

ESTROUSCYCLE

Presented by: Dr. ROHIT JUNEJA

(MVSc)

DEFINITIONS:

ESTROUS CYCLE:• Derived from Latin word oestrous (frenzy) and originally

from Greek (gadfly)

Estrous cycle comprises the recurring physiologic changes

that are induced by reproductive hormones in

most mammalian females.

Period from one estrus to the next.

Two phases:

Follicular Phase (proestrus and estrus)

Luteal phase(metestrus, diestrus )

http://en.wikipedia.org/wiki/Physiology

http://en.wikipedia.org/wiki/Reproductive_hormone



DEFINITIONS :

ESTRUS: Period of sexual receptivity.

• Commonly referred to as “Heat”

ANESTRUS: Period when female does not

showed estrous cycles

• Occurs during pregnancy etc.

• Cycle is categorized by frequency occurrencethroughout the year:

– Polyestrus: exhibit regular estrous cycles throughout

the year

• Example: Cattle, Swine, Rodents

TYPES OF ESTROUS CYCLE

• Seasonally polyestrus:

– Cycles occur only during certain times of the year/ exhibit estrous

cycle during a particular season

• Long-day breeders:

– Cycle when day length increases

Example: Mare

• Short-day breeders:

– Begin to cycle as day length decreases

»Example: “ Sheep, Goats “

• Monoestrus:

– One cycle per year

• Periods of estrus last for several days

– Example: Dogs, Wolves, Foxes, Bears,

wild animal, Elephant, Tiger.

PHASES OF ESTROUS CYCLE

• FOLLICULAR PHASE:

– Short phase - only 20% of cycle

– Period from regression of corpus luteum to

ovulation

– Preovulatory follicle

– Dominant hormone is estradiol

PHASES OF ESTROUS CYCLE

• LUTEAL PHASE:

– Long phase - 80% of cycle

– Period from ovulation to corpus luteum regression

– Corpora lutea

– Dominant hormone is progesterone

– Follicle continue to grow and regress during this

phase

STAGES OF ESTROUS CYCLE

• Four stages:

– Proestrus

– Estrus

– Metestrus

– Diestrus

• Follicular phase = Proestrus + Estrus

• Luteal phase = Metestrus + Diestrus

PROESTRUS

• Begins when progesterone

declines(luteolysis) and ends at onset of estrus

• Lasts 2 to 5 days

• Period of major endocrine transition

– Progesterone dominance to estrogen dominance

– FSH and LH responsible

“Building Up”

– Ovarian follicle, with enclosed ovum, increase in size

– Estrogens absorbed from the follicles into

blood stream stimulate increased vascularity

and cell growth of tubular genitalia, in

preparation for estrus and pregnancy

• Period of sexual receptivity

• Large increase in estrogen

– stimulates release of LHRH

• FSH decreases due to estrogen and inhibin

– During or shortly after estrus, ovulation

occurs due to major surge in LH

– LH levels increase due to LHRH

– Estrus stops once ovulation occurs.

• Corpus Luteum predominant

• ↑Increase in progesterone, ↆ decrease in estrogen

• Endometrial lining thickens and uterine

muscles show increased development.

• Relatively short period of time between

estrous cycles during the breeding season

of polyestrous animals

– No reproductive activity

• CL is fully functional*

• High levels of progesterone

• End with luteolysis

• 10 to 14 days (Depending on the species of animal)

*corpora lutea

• Proestrus= Formation of ovulatory follicle + E2 secretion

• Estrus = Sexual recepitivity + peak E2secretion

• Metestrus = CL formation + beginning of P4 secretion

• Diestrus = Sustained luteal secretion of P4

• Long period of inactivity between sexual seasons

– No regular estrous cycles

– Ovaries relatively inactive

• No follicles or CL

Average Reproductive Cycles

Species Length of

Estrous Cycle

Length of

Estrus

Ovulation Length of

Pregnancy

Cow 21 days 18 hr 11 hr after 282 dayspolyestrus end estrus

Ewe 17 days 29 hr near end 148 daysseasonal (fall) estrus

Sow 21 days 48-72 hr 35-45 hr 115 dayspolyestrus after start

estrus

Mare 21 days 4-8 days 3-6 day of 335 days seasonal (spring) estrus

polyestrus (1-2 days

before end of estrus)

The basic pattern of the estrous cycle is the same in all domestic animals, but

some specific differences are found in specific parts of the cycle. Some

specifics about relevant farm species are summarized in Table

ChChararacteacteririsstiticscsofofCharacteristics of Estrous Cycles

Cow Ewe Sow Mare

Estrous cycle (days) 21 17 21 21

Proestrus (days) 3-4 2-3 3-4 3-4

Estrus 12-18 hr 24-36 hr 48-72 hr 4-8 days

Metestrus (days) 3-5 3-5 3-4 3-5

Diestrus (days) 10-14 7-10 9-13 6-10

Variation in Cycle Types

Example Type of Cycle

Follicular Development

Ovulation & CL Formation

CLFunction

Cow, ewe, Long Spontaneous Spontaneous Spontaneous sow, mare

Rats, mice, Short Spontaneous Spontaneous Induced hamsters (4 days) (prolactin)

Rabbit, cat, Induced Spontaneous Induced Induced mink, ferret, (LH surge)otter, alpaca

Methods of Estrus Detection

Causes of Anestrus

Tail-painting & use of chalk

Use of closed circuit

television female activity

changes Progesterone testsVaginal probes

Use of teaser

animals Chin-male

devices Heat-

mount detectors

CL CL

Ovulation Atresia

ProgesteroneCA

EstradiolPGF2

FSH

LH

-7 - 6 - 5 - 4 - 3 - 2 -1 0 1 2 3 4 5 6 7 8Days Relative to the Gonadotropin Surge

Diestrus Proestrus Estrus Metestrus Diestrus

1

The estrous cycle

may be divided into

several phases based

on behaviour changes

or structural changes

in internal & external

genitalia.

Atresia

CL

CA

Ovulation

CL

Days Relative to the Gonadotropin Surge0 1 2 3 4 5 6 7 8-7 - 6 - 5 - 4 - 3 - 2 -1

FSH

LH

PGF2

Estradiol

Progesterone

Metestrus DiestrusProestrusDiestrus Estrus

Follicular Phase

Proestrus

• Follicle enlarges

• Estrogen increases

• Vascularity of the female reproductive tract increases

• Endometrial glands begin to grow

• Estrogen levels peak

2

Estrus

•

•

•

•

•

•

•

Allows male to mount

Estrogen decreases

LH surge occurs

Ovulation 24-48 h after surge of LH

Uterine motility high with contractions moving toward oviduct

Sperm transport is optimal

Cervical mucus volume increases

Follicular Phase3

Atresia

CL

CA

Ovulation

CL

Days Relative to the Gonadotropin Surge4 5 6 7 8

LH

-7 - 6 - 5 - 4 - 3 - 2 -1 0 1 2 3

FSH

PGF2

Estradiol

Progesterone


Luteal PhaseLuteal Phase

Metestrus

• Estrogen low

• Ovulation in cow

• Corpus hemorrhagicum present

• Uterus

Contractions subside

Endometrial glands continue to grow and become coiled

In cattle bleeding occurs

• FSH increases

Triggering growth of follicles

4

Atresia

CL

CA

Ovulation

CL

LH

-7 - 6 - 5 - 4 - 3 - 2 -1 0 1 2 3 4 5 6 7 8Days Relative to the Gonadotropin Surge

FSH

PGF2

Estradiol

Progesterone


Luteal PhaseLuteal Phase

Diestrus

• Progesterone high

• FSH

Increases at some point to cause growth of ovulatory follicle

• Uterus

Secrets fluid but volume gradually decreases

Contraction stop

CL regresses at the end of this period if female is not pregnant due to PGF release

5

Before heat

(6-10 h)

Hours 0 6

Hours from the start of estrus

9 18 24 28

Egg released

Life of egg

(6-10 h)

Standing heat

(18 h)After heat

(10 h)

Estrus in cow and associated featured

Approximate Values for Selected Reproductive Events in Female

Domesticated Mammals

SpeciesLength of

cycle (days)

Duration of estrus (hours) Approximate time of ovulation Normal breeding season

CowMean=20.5

Range 17 - 23Mean < 10

Range 1 - 2430 h after beginning of estrus All year

BuffaloMean=21

Range 18 - 22Mean < 15

Range 4 - 2432 h after beginning of estrus All year

Mare

Mean=21 Range 12 - 35

Mean=120 Range 24 - 240

Near end of estrus Spring & summer

Ewe


Mean=30 Range 20 -48

26 h after beginning of estrus Fall (variable with breed)

DoeMean=20

Range 16 - 22Mean=40

Range 24 - 72On 2nd day of estrus Fall

Sow



36 h after beginning of estrus All year

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